Matt Dillon wrote:
> :
> :I did it as part of the KSE work in 5.x. It would be quite easy to do it
> :for 4.x as well, but it makes a.out coredumps problematic.
> :
> :Also, "options UPAGES=4" is a pretty good defensive measure.
> :
> :Cheers,
> :-Peter
> :--
> :Peter Wemm - [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
>
> Well, in 4.x:
>
> (kgdb) print p->p_addr
> $6 = (struct user *) 0xcb7b9000
> (kgdb) print &p->p_addr->u_sigacts
> $7 = (struct sigacts *) 0xcb7b9260
> (kgdb) print &p->p_addr->u_stats
> $8 = (struct pstats *) 0xcb7b9cd0
> (kgdb) print &p->p_addr->u_kproc
> $9 = (struct kinfo_proc *) 0xcb7b9db0
> (kgdb) print &p->p_addr->u_md
> $10 = (struct md_coredump *) 0xcb7ba1d0
> (kgdb) print &p->p_addr->u_guard (my new field)
> $11 = (u_int32_t *) 0xcb7ba1d0
> (kgdb)
>
> cb7b9000 start of kstack
> cb7ba1d4 end of struct user
> cb7bb000 top of kstack
>
> Leaving us 3628 bytes for the kernel stack.
>
> Something really weird is going on... I added u_guard to the end
> of the struct user structure and there are two or three processes
> hitting the guard immediately. All the rest are ok. I'm going
> to investigate further but this is very odd. Am I missing something
> about the UAREA?
Yes. u_md etc isn't used while the process is running. If you're going to
have u_guard, it should come directly after u_stats, and *before* u_kproc,
u_md etc.
I had been contemplating making a fake 'struct user' in userland only in
order to keep the a.out coredump reader code happy. The a.out coredump
code (see cpu_coredump() in */*/vm_machdep.c) can generate this fake
structure in order to keep gdb happy. But then I realized that a.out
coredump debugging was almost totally irrelevant these days.
Actually I tell a lie. In 4.x, u_kproc *can* be used on a live process..
see the **NASTY** PT_READ_U and PT_WRITE_U code in sys_process.c. It does a
fill_eproc() in order to be able to read/write values from there. Nothing
uses this stuff. I removed it from -current quite a while ago, and it
should be MFC'ed too.
Cheers,
-Peter
--
Peter Wemm - [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
"All of this is for nothing if we don't go to the stars" - JMS/B5
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